An Electro-Hydraulic “Lost Motion” VVA System for a 3.0 Liter Diesel Engine

Fuel efficient thermal management of diesel engine aftertreatment is a significant challenge, particularly during cold start, extended idle, urban driving, and vehicle operation in cold ambient conditions. Aftertreatment systems incorporating NO xmitigating selective catalytic reduction and diesel oxidation catalysts must reach ;250°C to be effective. The primary engine-out condition that affects the ability to keep the aftertreatment components hot is the turbine outlet temperature; however, it is a combination of exhaust flow rate and turbine outlet temperature that impact the warm-up of the aftertreatment components via convective heat transfer. This article demonstrates that cylinder deactivation improves exhaust thermal management during both loaded and lightly loaded idle conditions. Coupling cylinder deactivation with flexible valve motions results in additional benefits during lightly loaded idle operation. Specifically, this article illustrates that at loaded idle, valve motion and fuel injection deactivation in three of the six cylinders enables the following: (1) a turbine outlet temperature increases from ;190°C to 310°C with only a 2% fuel economy penalty compared to the most efficient six-cylinder operation and (2) a 39% reduction in fuel consumption compared to six-cylinder operation achieving the same ;310°C turbine out temperature. Similarly, at lightly loaded idle, the combination of valve motion and fuel injection deactivation in three of the six cylinders, intake/exhaust valve throttling, and intake valve closure modulation enables the following: (1) a turbine outlet temperature increases from ;120°C to 200°C with no fuel consumption penalty compared to the most efficient six-cylinder operation and (2) turbine outlet temperatures in excess of 250°C when internal exhaust gas recirculation is also implemented. These variable valve actuation-based strategies also outperform six-cylinder operation for aftertreatment warm-up at all catalyst bed temperatures. These benefits are primarily realized by reducing the air flow through the engine, directly resulting in higher exhaust temperatures and lower pumping penalties compared to conventional six-cylinder operation. The elevated exhaust temperatures offset exhaust flow reductions, increasing exhaust gas-to-catalyst heat transfer rates, resulting in superior aftertreatment thermal management performance.

Section: Focus Of This Studymentioning

confidence: 89%

Section: Variable Valve Profilesmentioning

confidence: 99%

Fuel efficient exhaust thermal management for compression ignition engines during idle via cylinder deactivation and flexible valve actuation

Ding

Roberts

Fain

et al. 2015

“…The higher EGT and lower unburnt HC and CO were attained at low-load conditions by introducing internal exhaust gas recirculation (iEGR) with higher exhaust back pressures. [22][23][24] Other research into the use of a VVA to improve exhaust thermal management can be found in literatures. [25][26][27] The focus of this work is the exploration and direct comparison of different strategies for EGT management and the trade-off with fuel efficiency and emissions.…”

Section: Introductionmentioning

confidence: 99%

Exploring alternative combustion control strategies for low-load exhaust gas temperature management of a heavy-duty diesel engine

Guan

Zhao

Ban

et al. 2018

6The employment of aftertreatment systems in modern diesel engines has become indispensable 7 in order to meet the stringent emissions regulations. However, a minimum exhaust gas 8 temperature (EGT) of approximately 200°C must be reached to initiate the emissions control 9 operations. Low load engine operations usually result in relatively low EGT, which lead to 10 reduced or no exhaust emissions conversion. In this context, this study investigated the use of 11 different combustion control strategies to explore the trade-off between EGT, fuel efficiency 12 and exhaust emissions. 13 14The experiments were carried out on a single cylinder common rail heavy-duty diesel engine 15 at a light load of 2.2 bar indicated mean effective pressure. Strategies include the late intake 16 valve closure (LIVC) timing, intake throttling, late injection timing (Tinj), lower injection 17 pressure (Pinj), and internal exhaust gas recirculation (iEGR) as well as external EGR (eEGR) 18 were investigated. Results showed that the use of eEGR and lower Pinj were not effective in 19 increasing EGT. Although the use of late Tinj could result in a higher EGT, the delayed 20 combustion phase led to the highest fuel efficiency penalty. Intake throttling and iEGR allowed 21 for an increase in EGT by 42°C and 52°C at the expense of 7.2% and 17% fuel consumption 22 penalties, respectively. In comparison, LIVC strategy achieved the best trade-off between EGT 23 and ISFC, increasing the EGT by 52°C and the fuel consumption penalty by 5.3% while 24 reducing NOx and soot emissions simultaneously. When the IVC timing was delayed to after 25 -107 CAD ATDC, however, the combustion efficiency deteriorated, and hence very high HC 26 and CO emissions. This could be overcome by combining iEGR with LIVC to increase the in-27 cylinder combustion temperature for a more complete combustion. The results demonstrated 28 that the "LIVC + iEGR" strategy can be the most effective means, increasing the EGT by 62°C 29 with small penalty in the fuel consumption of 4.6% and soot emission reduction by 85%. 30 Meanwhile, maintaining high combustion efficiency as well as low HC and CO emissions of 31 diesel engines. 32 Keywords 33 Heavy-duty diesel engine, variable valve actuation, late intake valve closing, internal EGR, 34 exhaust temperature, exhaust emissions 35 36 42 combustion produces a large amount of particulate matter (PM) in the fuel rich burning region 43 and high concentration of nitrogen oxide (NOx) in the high temperature zones [1]. In order to 44 meet the Euro VI or equivalent emission regulations of 0.4 g/kW•h NOx and 0.010 g/kW•h PM 45 [2], significant reduction of these pollutants by in-cylinder combustion technologies and 46 emission control aftertreatment systems are required. 47 48 Advanced combustion modes such as Homogeneous Charge Compression Ignition (HCCI), 49 Pre-mixed Charge Compression Ignition (PCCI), and Low Temperature Combustion (LTC) 50 are able to achieve a reduction in NOx and soot simultaneously, through reducing the peak in-51...

“…28 Previous studies have concluded that there is a potential for EEVO to raise exhaust temperatures. [29][30][31][32] Wickstro¨m 31 noted an exhaust temperature increase with EEVO; however, this was not studied in detail due to the large fuel consumption penalty induced. Honardar et al 30 reported that exhaust valve phasing (a shift in both opening and closing timing) yielded a smaller exhaust temperature increase than a late post-injection strategy with a fuel consumption increase of 11%.…”

Section: Introductionmentioning

confidence: 99%

Modeling the impact of early exhaust valve opening on exhaust aftertreatment thermal management and efficiency for compression ignition engines

Roberts

Magee

Shaver

et al. 2014

In response to strict emissions regulations, engine manufacturers have implemented aftertreatment technologies to reduce the tailpipe emissions from diesel engines. The effectiveness of most of these systems is limited when exhaust temperatures are below 250°C. This is problematic during cold start and at low-load engine operation when the exhaust gas temperature is too low to keep the aftertreatment working effectively. The implementation of variable valve actuation strategies, including early exhaust valve opening, has been proposed as a means to elevate exhaust temperatures. Early exhaust valve opening results in hotter exhaust gas; however, more fueling is needed to maintain brake power output. This article outlines an analysis of the impact of early exhaust valve opening on exhaust temperature (measured at the turbine outlet) and the required fueling. An experimentally validated model is developed, which relates fueling increase with the timing of exhaust valve opening. This model is used to generate expressions for brake thermal efficiency and turbine out temperature as a function of exhaust valve opening. These expressions are used to evaluate the impact of early exhaust valve opening over the entire low-load operating space of a diesel engine. The model predicts an approximate 30°C-100°C increase in turbine out temperature at a given commanded exhaust valve opening of 90°b efore nominal, which is sufficient to raise many low-load operating conditions to exhaust temperatures above 250°C; however, the analysis also predicts penalties in brake thermal efficiency as large as 0.05 points.